A variety of different sole constructions are used by the footwear industry. For the most part, each sole construction has characteristics that make it particularly well-suited for specific applications. For example, some sole constructions are selected for their durability, others for their flexibility and comfort, while still others are selected for their aesthetic appeal.
One well-known type of shoe construction is referred to as a welt construction, which is typically a strip of material such as leather or hard rubber used to secure the sole and the upper together. Welt constructions generally provide durability and aesthetic appeal. FIG. 1 is a cross sectional view of a conventional Goodyear welt construction. This construction usually includes a welt 10 that connects an upper 12 and a sole 14. The welt 10 often includes a base portion 16 with an upwardly extending rib 18 located toward the center of the base portion and a downwardly extending rib 19 located at the inner edge of the base portion 16. The sole 14 may include an insole 20, a midsole 22, and an outsole 24. The insole 20 typically includes a downwardly extending rib 26 that is used to connect the insole 20, upper 12 and welt 10.
Welt construction typically involves a number of manufacturing operations or steps. Normally, the upper is wrapped around a last and secured to the insole by stapling, stitching, or other fastening mechanism. This step typically provides the upper with a desired shape and is commonly referred to as lasting. Once lasted, the welt is usually secured to the upper and insole by stitches or staples that extend through downwardly extending rib 19, the bottom periphery of the upper 12, and the insole rib 26. The midsole may be secured to the bottom of the upper/insole assembly. Typically, the midsole is attached to the upper/insole assembly by stitching that extends through the base portion 16 of the welt 10 and the midsole 22. Although this construction is believed to be durable and aesthetically appealing, it is generally a heavy construction and typically does not provide flexibility relative to other shoe constructions. Moreover, due to the number of manufacturing operations specified above, the cost of providing a welt construction shoe may be higher than other shoe constructions.
Cementing components of a shoe, such as the upper to the midsole or outsole, also often involves a number of manufacturing operations. Typically, there is a surface preparation step where the surfaces to be cemented, or glued, are clean of debris and readied, which may also include roughening. Further, there may be an application step where the cement is applied to the surfaces. This step may also involve measuring and evenly distributing the glue over the surface.
Further, there may be a pressing step where the surfaces are pressed together. Pressing is believed to reduce air that may be trapped between the surfaces and enhances adhesion. Pressing may also include aligning the surfaces so that the peripheries of the components are flush with one another. Once the components are pressed together, cementing often requires a waiting period for the cement to cure, or dry. Generally, not only does cementing involve some or all of the above mentioned manufacturing operations, it also involves time, particularly the curing time.
It is believed that the number of steps and time involved, especially if user intervention is required, negatively affects cost and efficiency. The cementing process may be further complicated if the surfaces to be glued are uneven or difficult to reach.
It is also well-known to construct shoes using an Opanka construction. In an Opanka construction, the outsole of the shoe is sewed to the upper of the shoe along an outer periphery of the outsole. The Opanka construction is described in currently pending U.S. Application Publication No. 2007/0062064. FIG. 2 shows a cross-sectional view of a shoe having an Opanka construction, where an upper 12 is secured to an outsole 14 using a thread 36 that passes through a plurality of holes in the upper 12 and the outsole 14. A channel 38 is provided on the outsole 14 to help prevent the stitched thread 36 from being worn quickly due to contact with the ground.
In the example shown in FIG. 2, it is apparent that the Opanka construction or stitching produces two rows of stitching: an upper row is formed on the outer periphery of the upper and a lower row is formed in the channel 38. In other Opanka-constructed shoes, the lower row is formed on a side of the outsole 14 so that it is visible along with the upper row. In still other Opanka-constructed shoes, one of the lower or upper rows of stitching will be formed on the inside of the upper, and thus will not be visible.
When constructing certain types of shoes, it is often desirable to vary the stitching pattern or the way in which the upper and outsole are joined between the front of the shoe and the back of the shoe. For example, in shoes that are intended for hiking or heavier outdoor use, it is often desirable to protect the stitching in the toe area from abrasion and wear. At the same time, it may be desirable to utilize an Opanka stitch wherein both an upper row and a lower row of the stitching are readily accessible on the outside of the shoe. Alternatively, it may be desirable for the upper to be folded inwards as it is joined to the outsole in the toe region and outwards as it joins the outsole in the heel region. Such variation between the toe of the shoe and the heel of the shoe may be desirable for various reasons, including, simplicity of design, simplicity of manufacturing, aesthetic appeal, and the like.
Previously, accomplishing such variation in a shoe caused a substantial increase in the cost of manufacturing such a shoe. This increase in cost was often due to the need to utilize two or more stitching techniques to accomplish the variation in shoe construction from the front of the shoe to the back of the shoe. For example, U.S. Pat. No. 4,250,638 to Linnemann appears to disclose a shoe construction in which the upper is folded inwards in the heel area and folded outwards in throughout the rest of the shoe. However, the upper is secured by a different stitch in each of the two different areas of the shoe: a backstitch is used in the heel and a pricking stitch is used around the rest of the shoe.
What is needed, therefore, is a shoe that may be constructed in a more efficient manner, by reducing manufacturing costs and involving fewer manufacturing operations, but that permits variation in the shoe construction in different portions of the shoe where the upper meets the outsole.